As a young boy, Eren Jaeger was experimented on by his father, Grisha. These tests aimed to improve on the Titan process, a military experiment that inadvertently transformed humans into giant beasts. Living in a decimated world caused by these Titans, Grisha was successful in bestowing on his children, Eren and Shikishima, an improved method. Implemented through an injected formula, their father had created "Jaeger" Titans. This gifted the children the ability to shift between human and Titan forms when exposed to life threatening or extremely stressful situations. When this happened, the Titan grew out of the human before enveloping them. The human form would stay relatively protected inside the back of the Titan's neck, while the individual would be able to control most of the creature's actions. This process also healed the individual, granting them briefly the regenerative powers of the Titans.

These experiments were done in secret, as Grisha, assisted by Souda and his wife Carla, conducted them out of his house. However, they eventually arose the suspicion of the Military Police. As they stormed the home, Souda narrowly escaped with Eren, while the boys' parents were captured. His brother, Shikishima, was also separated from his sibling, as Eren grew up unaware of their relation.

Years passed as Eren matured in the Monzen District, found inside a walled area of Japan. Built with multiple layers, this area protected them from the Titans beyond. As years of peace transpired, fear of the Titans began to diminish from the younger generation. This included Eren, who was unaware of his ability to transform into a Titan himself. Together with his friends Armin Arlert and Mikasa Ackerman, the trio ventured to the outer most wall. With a case of wanderlust, including the desire to see the ocean, the group mused over leaving the walled area. They were stopped, though, by Souda, who ran a garrison to protect the barrier. However, their conversation was interrupted by small tremors. The source of the quakes revealed itself, as the Colossal Titan peeked over the barrier. Standing 120 meters tall, the creature attacked, creating a large hole in the wall. The beast then vanished in a cloud of steam, yet the aftermath of its actions would be horrific.

From the large hole, Titans appeared, drawn by their desire to consume. The garrison engaged them, but quickly fell, eaten by the monstrosities. Eren, Armin and Mikasa fled to the town area, but the Titans quickly advanced on them. The horrors walked around, grabbing and feasting on humans as they went. Familiar faces to the three died in horrible ways, including Armin's parents. Hysteria kicked in as crowds frantically moved in every direction to avoid a grisly fate.

Among the confusion, Mikasa spotted a baby and attempted to rescue it. This, however, caused her to be separated from the others as Eren was pushed into a building. Frantically, Eren attempted to reunite with Mikasa, but those in the building pushed him back, trying to save themselves from the Titans. To his horror, a female Titan spotted Mikasa and the baby. The beast advanced, reaching down to bite and feast them. Meanwhile, Eren broke through the building, although was unable to locate Mikasa. As he left, Titans broke through the building behind him, killing the humans inside.

Two years later, the survivors had escaped into the inner walled area. Since the incident, humanity had attempted to fill the hole and reclaim their lost land. Sending out regiments, the efforts had been unsuccessful due to the Titans. Humanity had also advanced their tactics, attempting to become more adept at killing Titans. This included the discovery of their weakness, the nape, and weapons to attack it, the omni-directional mobility (ODM) gear. These tools released anchors into buildings, allowing their user to travel in the air and get high enough to slash a Titan's neck area.

Eren, along with Armin, had joined a regiment to go on one of these expeditions to fix the hole. The two friends reunited with Souda, who was also part of the regiment. He was given the grim news of Mikasa's fate.

Briefed, the regiment disembarked, heading for Omote City. There they planned to secure an explosive stockpile, the last humanity had access to. The strategy to seal the hole was to use the explosives to detonate the top of the wall, having it collapse and cover the breach.

Moving at night, to take advantage of the Titans' poor vision, the group traveled by vehicle. Among their rank was the director of the Military Police, Kubal, as the feeling was this was their last chance to seal the hole. While traveling, they group stopped to scout the area, sensing something nearby. This turned out to be cows, for whom the Titans had no interest in eating.

Feeling there was no threat, the group decided to push on, although one member, Hiana, claimed to hear crying. As she rushed off, Eren followed. Together, they stumbled upon the source: an infant Titan. The monster, who had been chewing on a human, attempted to attack the two, but they easily evaded it. Angry, the baby cried out, alerting adult Titans.

As Eren and Hiana ran back to the group, Titans swarmed in. The group's captain warned against making noise, which would alert the beasts, but was too late as he was grabbed by a nearby Titan. Seeing the severity of the situation, the director ordered the vehicles to continue on, abandoning Eren, Armin and others.

After a great struggle and heavy losses, Eren and the others eventually managed to reach Omote City. However, a Titan blocked their path. The beast was slaughtered, though, by Shikishima using the ODM gear, who had suddenly appeared. As another Titan emerged, it too was killed, this time by Mikasa. As it turned out, she survived the Titan siege two years ago. However, the baby she was holding did not, while Mikasa had a huge scar left from the Titan's bite. Since then, she had become chief to Shikishima, who was captain of a scout regiment.

Shortly afterwards, the survivors regrouped with the vehicles and together they gathered the explosives. Once alone, Shikishima asked Eren for his name. The captain then quickly realized their relation, although didn't tell Eren this. He then asked the young man about their parents, as Eren lamented that they died when he was very young. However, Eren was more interested in learning about Mikasa, as Shikishima noted that he was the one that trained her to slay Titans. He offered to similarly train Eren, but asked why he hated Titans. Learning it was because they trapped humanity behind the walls, Shikishima scoffed and claimed it was safety that led to this.

Later, the regiment established camp in a nearby demolished building, preparing to venture to the wall after resting. However, the group was ambushed by the Titans. Attacking both Hiana and Eren, the former was eaten as Eren helplessly watched.

Quickly, Shikishima and Mikasa engaged the Titans, using the ODM to slash their necks. During the confusion, though, the explosives were lost, first stolen and then detonated in a suicide run against the Titans. As more and more of his comrades are devoured, Eren, in a rage, used his ODM to fly at the Titans. He managed to land a killing blow, yet he became distracted from slaying one of them. As a result, another Titan was able to bite off his leg in midair, sending him collapsing on top of a nearby building. Shikishima, seeing his brother's defeat, emotionlessly noted that sometimes people were unlucky.

Meanwhile, other members of the regiment were trying to save a stranded soldier. Amidst the chaos, though, Armin was grabbed by one of the creatures. Eren, seeing his friend in danger, rushed in time to save him, literally throwing him out of the beast's mouth. In retaliation, though, the monster bit off Eren's arm and swallowed him. Once inside the creature, Eren found the half digested corpse of Hiana and screamed, consumed by rage.

As Eren screamed inside it, the Titan advanced on Mikasa. Stranded on the ground, out of gas for her ODM, she watched as the Titan walked toward her. However, the beast stopped and contorted in pain. Emerging from its mouth, two giant hands reached out and ripped the creature in half from the inside. Standing amidst the gore was the Attack Titan. Bellowing a challenge, the monster went into a frenzy. Running up to a Titan, the rogue creature attacked it. As the Titan started to heal, the rogue beast killed it, drawing the attention of the other Titans in the process. The Attack Titan proved too powerful, though, as it went around easily killing the others by smashing their heads with his fists.

Having felled his enemies, the beast briefly threatened the group of survivors before it collapsed. Realizing what happened, that this was the Jaeger Titan he helped Grisha create many years ago, Souda ordered them to slash the nape. He feared that if he it stayed in this form too long it would absorb Eren. Following the order, Mikasa slashed free her former friend, causing the Attack Titan to disappear. Shikishima observed this as well, realizing he was not alone in being a Jaeger Titan.

Later, Eren was chained up and questioned by the director. Asked if he is a Titan or a human, the director ignored his response that he was human. Noting that he regrew limbs, the director ordered the young man's execution. His friends attempted to defend him, with Armin stating how he fought for them and killed other Titans. Others vouched for him as well, including Souda, who began to describe where Titans came from. However, the director quickly shot and killed Souda before he could explain, revealing darker intentions.

He then reiterated the order to kill Eren. Suddenly, though, the ceiling collapsed, and the Armored Titan landed in front of them. As the debris lands around it, the director was seemingly crushed. Another soldier, Hans, then declared command and ordered the others to stand down. They attacked the Armored Titan, though, who managed to grab and rescue Eren, leaving the area.

Later, Eren awoke to find himself in a white room. Emerging from the shadows, Shikishima offered his brother champagne. He then told his younger sibling where Titans came from, that they were a military experiment gone wrong.
Shikishima then noted how the ruling class had then used the beasts as a tool of fear, keeping humanity trapped. Proposing an alliance, the two joined forces.

Together, with the remnants of a Scout Regiment loyal to Shikishima, they confronted the survivors. Led by Hans, they discovered that the group had secured another explosive, a relic that existed in Monzo. Shikishima was glad, but informed them it would not be used to seal the wall. Instead, it would be used to break down the inner wall, ending the reign of the ruling class. Realizing his intent and the sheer amount of lives that would be lost, Eren denounced their alliance. The two brothers fought before their fight was broken up. One of the soldiers then caused a nearby building to collapse, falling on a nearby tank and causing an explosion that wiped out Shikishima's secret guard.

In response, Shikishima stabbed himself with his own sword, causing him to transform into the Armored Titan. The group then realized the identity of the armored beast, while Eren announced that he wanted to fight it as a Titan. The others convinced him to instead help them attack the beast using their ODMs. Using explosive arrows, the group managed to successfully attack the Armored Titan, but failed to hit the nape. As the armored creature came close to killing one of the soldiers, Eren rescued them by sacrificing himself. Rather than killing Eren, though, the stress caused him to transform into the Attack Titan.

The two giants become locked in combat, although the Armored Titan proved stronger. However, the Attack Titan kicked his foe in the face, and then evened the odds by grabbing a large pole. Using it, he skewered his older brother, defeating him.

The rogue Titan then secured the bomb as Armin put a timer on it. Climbing the wall, he attempted to put the bomb in position. However, the rogue Titan began to slow its ascent, as fear mounted that Eren would be absorbed. Mikasa leaps on the monster's back and used her sword to create an incision in the neck, accidentally slashing Eren's human hand in the process. She called to Eren, eventually telling that she wanted to be with him and see the ocean. As memories flood back to him, Eren regained his senses and the Attack Titan continued to climb again. Placing the explosive in position, the beast roared as it reverted again to his human form.

Armin then activated the bomb to detonate in five minutes, as the group heard a man applauding them. They turned to see the director, Kubal, clapping. He then offered them a chance among the ruling class, although in return they had to turn over Eren to him. As the group refused, Kubal responded by shooting Armin in the leg. He then tried once more to convince them, although Eren countered stating that they will see the outside world. A soldier then shot the director in the chest with an arrow, but this triggered a transformation. As it turned out, Kubal was the Colossal Titan and set all of this in motion.

The group then tried to kill the mammoth Titan by cutting its nape. As it towered over everything, the beast tried to grab Eren, but was blasted in the face by an RPG from Hans. Eren then went on the offensive, trying to destroy the beast's nape with his sword, but failed. The colossal beast then tried to get the bomb, and while unsuccessful it managed to damage it enough to stop the timer from working. Suddenly, Shikishima appeared and, after a conversation with Mikasa, was convinced to help seal the wall.

Meanwhile, Eren got close to destroying the giant beast's nape, but was grabbed. As the Colossal Titan prepared to smash him, Eren's older brother, in his Armored Titan form, leapt at the giant beast. With the bomb in his grasp, the armored monster tossed the explosive at the director. The resulting explosion sent debris soaring, including sealing the hole in the wall. As Eren fell, Mikasa leapt and saved him.

Victorious, Eren and Mikasa stood on top of the wall, staring out at the ocean and the world beyond.

Powers / Weapons

Super Regenerative Power

The Attack Titan could quickly heal from severe levels of damage. While healing, large amounts of steam would be released from the injured area as the body heated as part of the regenerative process.

These regenerative abilities were also passed down to the human form of the Attack Titan as part of the transformation process. This included an instance where Eren's severed leg was completely healed.

Weaknesses

Nape

Located in the rogue Titan's nape was Eren's human body. As a result, and similar to other Titans, this created a weak point for the monster. In the event the area was damaged or destroyed, the Attack Titan would be defeated.

In two instances, Mikasa attacked this area of the creature. One was to free Eren, which dissolved the Attack Titan. The second instance was when the rogue Titan started to lose focus, and a smaller incision was made, allowing Eren to hear better and snap him into focus.

Background and Trivia

Although it's unknown how large the movie version is, the manga version of the Attack Titan is 15 meters in height according to the Attack on Titan Character Directory (ISBN: 4065102162). However, the creature seems to be of comparable size in the movie to the other Titans, who were 7 meters in height.

In Attack on Titan: End of the World (ISBN: 1945054085), a novelization of the two films, the Attack Titan is called the Mysterious Titan (謎の巨人 - Nazo no Kyojin).